Human cancers harbor numerous genetic and epigenetic alterations, generating neoantigens potentially recognizable by the immune system (Sjoblom et al. (2006) Science 314:268-74). The adaptive immune system, comprised of T and B lymphocytes, has powerful anti-cancer potential, with a broad capacity and exquisite specificity to respond to diverse tumor antigens. Further, the immune system demonstrates considerable plasticity and a memory component. The successful harnessing of all these attributes of the adaptive immune system would make immunotherapy unique among all cancer treatment modalities.
Recently, several immune checkpoint pathway inhibitors have begun to provide new immunotherapeutic approaches for treating cancer, including the development of an antibody (Ab), ipilimumab (YERVOY®), that binds to and inhibits Cytotoxic T-Lymphocyte Antigen-4 (CTLA-4) for the treatment of patients with advanced melanoma and the development of antibodies such as nivolumab and pembrolizumab (formerly lambrolizumab; USAN Council Statement (2013) Pembrolizumab: Statement on a nonproprietary name adopted by the USAN Council (ZZ-165), Nov. 27, 2013) that bind specifically to the Programmed Death-1 (PD-1) receptor and block the inhibitory PD-1/PD-1 ligand pathway.
Immune checkpoint antibodies can be administered in combination with other antibodies. Nonetheless, administering two antibodies can be burdensome due to different dosing and dosing interval between two antibodies, thereby causing multiple intravenous injections at different time points. Furthermore, two antibodies can have drastically different stability profiles. Due to the unique nature of each antibody, e.g., variations in Fc glycosylation, partial heavy chain C-terminal Lys processing, Fc methionine oxidation, hinge-region cleavage, and glycation of Lys residues, each antibody has varied physicochemical and/or thermodynamic properties, e.g., different degradation profiles when exposed to heat, freezing, light, pH extremes, agitation, sheer-stress, some metals, and organic solvents. Therefore, while a single formulation containing two antibodies would improve convenience, the unique nature of each antibody makes such a single formulation difficult to identify.